The Valsalva manoeuvre as a test of the cardiac response to sympathetic stimulation

The object of the investigation was to find a simple test of cardiac function, using established methods, sufficiently sensitive to detect deterioration of function before the advent of clinical signs of heart failure. It was hoped, by comparing the heart rate response to stress with changes in the systolic time intervals, to be able thereafter to use the heart rate response alone. The systolic time intervals have been noted to change with alterations in stroke volume, rate of flow and contractility. The most appropriate method of measuring these intervals, and the interpretation of these changes, was not altogether clear when the investigation was begun in July, 1969. Assumptions had therefore been made, based on the evidence available, and more recent work in the literature has proved these assumptions to be justified. These references, which refer to the use and significance of the pre-ejection period, ejection period and total systole, corrected for heart rate, have been included in the text. A small pilot study was undertaken to determine whether change of posture, release of venous cuffs or leg raising could be employed as the stress but the results were inconclusive. A difference was then found between subjects in the time of the return of heart rate after the Valsalva manoeuvre and this was preceded by a change in a systolic time interval. Relevant factors were therefore reviewed and a plan of work designed. It was concluded from the reviews that, if the heart reacted to changes in filling pressure by changes in stroke volume, then the ability to eject the blood rapidly in the presence of the resistance to flow induced by the manoeuvre would depend on the cardiac response to sympathetic stimulation. This would be reflected independently in the heart rate and systolic time intervals, corrected for heart rate. After the manoeuvre the heart rate and corrected ejection period and total systole rose and then fell. But the time intervals altered to an unexpected degree and in a manner suggesting they were affected by the rise and fall of pressure and resistance. However, compared with control subjects, in patients with ischaemic heart disease corrected total systole and ejection periods increased more and - together with the heart rate - fell more slowly to their resting levels. In a larger series, the heart rate response alone (number of beats from onset of fall to control heart rate) differentiated control subjects from patients. The probable causes of these differences and the application of the findings are discussed.